Multiple causes?
I have just finished reading “Comet” by Carl Sagan and Ann Druyan, revised 1997. It contains lots of interesting info about the behavior and size of comets and past and future damage potential for earth. We may be entering a period of more than average activity. Comets even if they are just an airy “snowball” can be seriously disasterous if they are large enough. “The Cycle of Cosmic Catastrophes”, Firestone, et al., 2006, hypothesizes a 300 mile diameter snowball crashing into what became Hudson Bay about 13,000 years ago, destroying the Clovis Indian culture, decimating the large mammal population, and precipitating the 1,000 years of cold called the Younger Dryas. This study also highlights the fact that these extraterrestrial bodies often come in groups as we saw with Shoemaker-Levy strikes on Jupiter recently.
The 34 mya Chesapeake Meteor event, with its 50 mile diameter crater, also coincided with the 60 mile diameter Popigai (sp?) crater in Siberia, the 9 mile Toms River (NJ) crater and a 10 mile crater in Spain.
Regarding the Permian extinction, this newly discovered crater at Antartica could also have occurred along with the better known Bedout crater near Australia. They both occurred enough opposite the Gigantic Siberian Trapps (4 or 5 times the volume of the Deccan) to have caused a reverberation effect through the earth.
It has also been hypothesized that there is a crater 4 or more times larger than the Yucatan crater called Shiva that was of the same time period. This crater appears to be on the West side of India, and if it exists could have been an immediate cause of the Deccan activity. For all we know a large boloid could have struck Siberia and been covered by the Siberian Trappes. Has anyone encountered any recent information about this controversial crater?
“The Jan/Feb 98 Issue of Planetary Report has an article by Michael Rampino “The Shiva Hypothesis”. This describes a 30 million year cycle of mass extinctions over the past 540 million years (see diagram). One hypothesis is that this corresponds the the solar system oscillating through the galactic plane as it orbits the Milky Way. Rampino notes that the last crossing of the galactic plane occurred a few million years ago and it has been suggested that this led to a disturbance of comets in the Oort Cloud, some of which could now be approaching the inner solar system.”
Our next trip through the Galactic plane: 2012AD
Fascinating. Maybe the Mayans are right?
The absence of an irridium rich layer at the Permian extinction, and the lack of shocked quartz and other impact related minerals and features (such as shock cones in rock) argue against a major impact triggering the Siberian flows.
Still, one can't help but wonder...